Compact, high-efficiency thermoelectric systems

ABSTRACT

A number of compact, high-efficiency thermoelectric system utilizing the advantages of thermal isolation in the direction of a working medium flow or movement, in manufacturable systems, are described. Such configurations exhibit high system efficiency and power density. Several different embodiments and applications are disclosed utilizing a plurality of thermoelectric modules or thermoelectric elements sandwiched between heat exchangers.

CONTINUING APPLICATION DATA

This application is a continuation in part of U.S. patent applicationSer. No. 09/844,818, filed Apr. 27, 2001 now U.S. Pat. No. 6,539,725,which is related to and claims the benefit of U.S. Provisional PatentApplication No. 60/267,657 filed Feb. 9, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This disclosure relates to improved configurations for solid-statecooling, heating and power generation systems.

2. Description of the Related Art

Thermoelectric devices (TEs) utilize the properties of certain materialsto develop a temperature gradient across the material in the presence ofcurrent flow. Conventional thermoelectric devices utilize P-type andN-type semiconductors as the thermoelectric material within the device.These are physically and electrically configured in such a manner thatthe desired function of heating or cooling is obtained.

The most common configuration used in thermal electric devices today isillustrated in FIG. 1. Generally, P-type and N-type thermal electricelements 102 are arrayed in a rectangular assembly 100 between twosubstrates 104. A current, I, passes through both element types. Theelements are connected in series via copper shunts 106 saddled to theends of the elements 102. A DC voltage 108, when applied, creates atemperature gradient across the TE elements. TEs are commonly used tocool liquids, gases and objects.

Solid-state cooling, heating and power generation (SSCHP) systems havebeen in use since the 1960's for military and aerospace instrumentation,temperature control and power generation applications. Commercial usagehas been limited because such systems have been too costly for thefunction performed, and have low power density so SSCHP systems arelarger, more costly, less efficient and heavier than has beencommercially acceptable.

Recent material improvements offer the promise of increased efficiencyand power densities up to one hundred times those of present systems.

SUMMARY OF THE INVENTION

Efficiency gains for geometries described in co-pending patentapplication Ser. No. 09/844,818 entitled Improved EfficiencyThermoelectrics Utilizing Thermal Isolation, yield an additional 50% to100% improvement for many important applications. Combined with thematerial improvements being made, system efficiency gains of a factor offour or more are possible. The prospects of these substantialimprovements have lead to renewed interest in the technology and theeffort to develop SSCHP systems for new applications.

In general, this disclosure describes a new family of SSCHPconfigurations. These configurations achieve compact, high-efficiencyenergy conversion and can be relatively low cost. Generally, severalembodiments are disclosed wherein thermoelectric elements or modules orare sandwiched between heat exchangers. The thermoelectric modules areadvantageously oriented such that for any two modules sandwiching a heatexchanger, the same temperature type side faces the heat exchanger. Forexample, the cooler side of each of the thermoelectric sandwiching aheat exchanger face the same heat exchanger, and thus each other.Preferably, at least one working medium is passed sequentially throughat least two heat exchangers so that the cooling or heating provided isadditive on the working medium. This configuration has the added benefitthat it utilizes the advantages of thermal isolation, as described inU.S. patent application Ser. No. 09/844,818, in manufactureable systemsthat exhibit high system efficiency and power density as noted in thereferences above. As explained in that application, in general, athermoelectric device achieves increased or improved efficiency bysubdividing the overall assembly of thermoelectric elements intothermally isolated subassemblies or sections. For example, the heatexchangers may be subdivided so as to provide thermal isolation in thedirection of working medium flow. For example, a thermoelectric systemhas a plurality of thermoelectric elements forming a thermoelectricarray with a cooling side and a heating side, wherein the plurality ofthermoelectric elements are substantially isolated from each other in atleast one direction across the array. Preferably, the thermal isolationis in the direction of the working media flow. This thermal isolationcan be provided by having a heat exchanger configured in sections suchthat the heat exchanger has portions which are thermally isolated in thedirection of working fluid flow.

In the present disclosure, having sequential use of heat exchangers ofthe same temperature type for the working fluid provides a type ofthermal isolation in itself. In addition, the heat exchangers or the TEelements, or portions of TE elements or any combination may beconfigured to provide thermal isolation in the direction of the workingfluid flow over and above the thermal isolation provided by having aseries or sequence of heat exchangers through which at least one workingfluid passes in sequence.

The principles disclosed for cooling and/or heating applications, areequally applicable to power generation application. The system may betuned in a manner to maximize the efficiency for the given application,but the general principles apply.

The particular embodiments described in this application lower theconstruction complexity and cost of SSCHP devices while stillmaintaining or improving efficiency gains from thermal isolation.

A first aspect of the present disclosure involves an improvedthermoelectric system having a plurality of thermoelectric modules, atleast some of which are substantially thermally isolated from eachother, each module having a hotter side and a colder side. At least onesolid working medium is in thermal communication with at least two ofthe plurality of thermoelectric modules in sequence, such that theworking medium is progressively cooled or heated in stages by at leasttwo of the thermoelectric modules.

In one preferred embodiment, the working medium comprises a plurality ofdisk-like media mounted to a rotating shaft, and the media form astacked configuration with the thermoelectric modules sandwiching atleast some of the disk-like media. Advantageously, the working mediummay comprise a plurality of working media forming an alternating stackedconfiguration of thermoelectric modules and working media. Preferably,the working media substantially thermally isolates at least some of theplurality of thermoelectric modules.

Another aspect of the present invention involves an improvedthermoelectric system having a plurality of thermoelectric modules, atleast some of which are substantially thermally isolated from eachother, each module having a hotter side and a colder side. A pluralityof heat transfer devices, each in thermal communication with at leastone of the plurality of thermoelectric modules are also provide, whereinat least two of the heat transfer devices accept a first working fluidthat travels through the heat transfer devices. At least one conduitcouples the at least two of the heat transfer devices in differentplanes, such that the first working fluid moves through a first of theat least two heat transfer devices and sequentially through a second ofthe at least two heat transfer devices, and is cooled or heated instages as it passes through the at least two heat transfer devices.

In one embodiment, each of at least some of the heat transfer devices issandwiched between at least two thermoelectric modules. In addition,preferably, at least two thermoelectric modules have the cooler sidefacing the sandwiched heat transfer device.

In one embodiment, the thermoelectric modules and heat transfer devicesform a stack, with cooler sides facing cooler sides, separated by atleast one heat transfer device, and hotter sides facing hotter side,separated by at least one heat transfer device.

In one embodiment, the heat transfer devices are heat exchangerscomprising a housing and heat exchanger fins, the heat exchanger finsforming stages in the direction of the working fluid flow, so as toprovide additional thermal isolation for at least one of thethermoelectric modules in thermal communication with the heat exchanger.Preferably, at least one conduit is configured such that working fluidflows through the at least two heat transfer devices couple by theconduit flows in the same direction.

Yet another aspect of the present invention involves a thermoelectricsystem having a plurality of N-type thermoelectric elements and aplurality of P-type thermoelectric elements. A plurality of heattransfer devices, at least some of which are each sandwiched between atleast one of the N-type thermoelectric elements and at least one of theP-type thermoelectric elements, are provided so as to form a stackedconfiguration of thermoelectric elements and heat transfer devices. Inone embodiment, the system further has a current source electricallycoupled to the stack, the drive current traversing through the heattransfer devices and thermoelectric elements in series. Preferably, theheat transfer devices thermally isolate at least some of the P-typethermoelectric elements from at least some of the N-type thermoelectricelements. Advantageously, the heat transfer devices accept a workingfluid to flow through them in a defined direction

In one embodiment, the heat transfer devices are heat exchangerscomprising a housing with heat exchanger elements inside formed insegments, and wherein at least one of the segments is substantiallythermally isolated from at least one other of the segments.

In one embodiment, the at least one conduit provides a fluid path from afirst heat exchanger to a second heat exchanger, such that working fluidtravelling through the first heat exchanger and the second heatexchanger is cooled or heated in stages.

These and other aspects and embodiments of the present invention aredescribed in more detail in conjunction with the Figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a conventional TE module.

FIG. 2 depicts a general arrangement of a SSCHP system with thermalisolation and counter flow movement of its working media.

FIG. 3 depicts the temperature changes that occur in the media, as theworking media progress through the system.

FIG. 4 depicts a system with three TE modules, fin heat exchangers andliquid-working media.

FIG. 5 depicts a system with two TE modules, segmented heat exchanger toachieve thermal isolation and counter flow of the liquid media,

FIG. 6 depicts and gaseous media system with two TE modules and ductedfans to control fluid flow.

FIG. 7 depicts a solid media system with counter flow to further enhanceperformance. The TE elements utilize a high length to thickness ratio toachieve added thermal isolation.

FIG. 8 depicts a system with TE elements arranged so that current passesdirectly through the array and thereby lowers cost, weight and sizewhile providing improved performance.

FIG. 9 depicts a system with TE elements, heat pipes and heat exchangersthat is simple and low cost. The hot side and cold side are separated bythermal transport through heat pipes.

FIG. 10 depicts a fluid system in which the fluid is pumped through theheat exchanger and TE module array so as to achieve a low temperature atone end to condense moisture out of a gas or a precipitate from a liquidor gas. The system has provisions to shunt working fluid flow to improveefficiency by lowering the temperature differential across portions ofthe array.

FIG. 11 depicts an array in which working fluid enters and exits at avariety of locations, and in which part of the system operates incounter flow and part in parallel flow modes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the context of this description, the term thermoelectric module or TEmodule are used in the broad sense of their ordinary and accustomedmeaning, which is (1) conventional thermoelectric modules, such as thoseproduced by Hi Z Technologies, Inc. of San Diego, Calif., (2) quantumtunneling converters, (3) thermoionic modules, (4) magneto caloricmodules, (5) elements utilizing one, or any combination ofthermoelectric, magneto caloric, quantum, tunneling and thermoioniceffects, (6) any combination, array, assembly and other structure of (1)through (6) above. The term thermoelectric element, is more specific toindicate individual element that operate using thermoelectric,thermoionic, quantum, tunneling, and any combination of these effects

In the following descriptions, thermoelectric or SSCHP systems aredescribed by way of example. Nevertheless, it is intended that suchtechnology and descriptions encompass all SSCHP systems.

Accordingly, the invention is introduced by using examples in particularembodiments for descriptive and illustrative purposes. A variety ofexamples described below illustrate various configurations and may beemployed to achieve the desired improvements. In accordance with thepresent description, the particular embodiments and examples are onlyillustrative and not intended in any way to restrict the inventionspresented. In addition, it should be understood that the terms coolingside, heating side, cold side, hot side, cooler side and hotter side andthe like, do not indicate any particular temperature, but are relativeterms. For example, the “hot,” side of a thermoelectric element or arrayor module may be at ambient temperature with the “cold,” side at acooler temperature than the ambient. The converse may also be true.Thus, the terms are relative to each other to indicate that one side ofthe thermoelectric is at a higher or lower temperature than thecounter-designated temperature side.

FIG. 2 illustrates a first generalized embodiment of an advantageousarrangement for a thermoelectric array 200. The array 200 has aplurality of TE modules 201, 211, 212, 213, 218 in good thermalcommunication with a plurality of first side heat exchangers 202, 203,205 and a plurality of second side heat exchangers 206, 207 209. Thedesignation first side heat exchanger and second side heat exchangerdoes not implicate or suggest that the heat exchangers are on one sideor the other side of the entire SSCHP system, but merely that they arein thermal communication with either the colder side or the hotter sideof the thermoelectric modules. This is apparent from the figure in thatthe heat exchangers are actually sandwiched between thermoelectricmodules. In that sense, they are in thermal communication with a firstside or a second side of the thermoelectric modules. The colder side ofa first TE module 201 is in thermal contact with a first side heatexchanger 205 and the hot side of the TE module 201 is in thermalcontact with an inlet second side heat exchanger 206. A second workingmedia 215, such as a fluid, enters the array 200 in the upper right handcorner of FIG. 2 through the inlet second side heat exchange 206, andexits near the lower left from a final or outlet second side heatexchanger 209. A first working media 216 enters at the upper leftthrough an inlet first side heat exchanger 202 and exits near the lowerright from a final or outlet first side heat exchanger 205. Electricalwires 210 (and similarly for other TE Modules) connected to a powersupply, not shown, connect to each TE module 201. First conduits 208,represented as lines on FIG. 2, convey the second working media 215 andsecond conduits 204 convey the first working media 216 sequentiallythrough various heat exchangers 202, 203, 205, 206, 207 and 209 asdepicted.

In operation, the second working media 215 absorbs heat from the TEmodule 201 as it passes downward through the inlet second side heatexchanger 206. The second working media 215 passes through conduit 208and upwards into and through the second side heat exchanger 207. In goodthermal communication with the heat exchanger 207 are the hotter sidesof the TE modules 211 and 212, which have been configured so that theirrespective hotter sides face toward one another to sandwich the secondside heat exchanger 207. The second side working media 215, is furtherheated as it passes through the second side heat exchanger 207. Thesecond side working media 215 next passes through the second side heatexchanger 209, where again, the hotter sides of the TE modules 213 and218 sandwich and transfer heat to the second side heat exchanger 209,further heating the second side working media 215. From the heatexchanger 209, the second working media 215 exits the array 200 from theoutlet or final second side heat exchange 209.

Similarly, the first working media 216 enters the inlet first side heatexchanger 202 at the upper left corner of FIG. 2. This heat exchanger202 is in good thermal communication with the colder side of the TEmodule 218. The first working media 216 is cooled as it passes throughthe inlet first side heat exchanger 202, on through another first sideexchanger 203 and finally through the outlet first side heat exchanger205, where it exits as colder working media 217.

The thermoelectric cooling and heating is provided by electrical powerthrough wiring 210 into TE module 218, and similarly into all the otherTE modules.

Thus, in sum, working media is placed in good thermal contact with thecold side of the TE module at the left hand side of the array, so thatheat is extracted from the media. The media then contacts a second andthird TE module where additional heat is extracted, further cooling themedia. The process of incremental cooling continues, as the mediaprogresses to the right through the desired number of stages. The mediaexits at the right, after being cooled the appropriate amount.Concurrently, a second media enters the system at the far right and isincrementally heated as it passes through the first stage. It thenenters the next stage where it is further heated, and so on. The heatinput at a stage is the resultant of the heat extracted from theadjacent TE modules' cold sides, and the electrical power into thosemodules. The hot side media is progressively heated as it moves in ageneral right to left direction.

In addition to the geometry described above, the system provides benefitif both media enter at the same temperature and progressively get hotterand colder. Similarly, the media can be removed from or added to thecool or hot side at any location within the array. The arrays can be ofany useful number of segments such as 5, 7, 35, 64 and larger numbers ofsegments.

The system can also be operated by reversing the process with hot andcold media in contact with TE modules, and with the hot and cold mediamoving from opposite ends (as in FIG. 2 but with the hot media enteringas media 216 and the cold media entering as media 215). The temperaturegradient so induced across the TE modules produces an electric currentand voltage, thus converting thermal power to electrical power. All ofthese modes of operation and those described in the text that followsare part of the inventions.

As illustrated in FIG. 2, the separation of the heat exchanger into asequence of stages provides thermal isolation in the direction of flowof the working media from TE module to TE module. U.S. patentapplication Ser. No. 09/844,818, entitled First Improved EfficiencyThermoelectrics Utilizing Thermal Isolation, filed Apr. 27, 2001describes in detail the principles of thermal isolation which areexhibited throughout this description with various specific andpractical examples for easy manufacturing. This patent application ishereby incorporated by reference in its entirety.

As described in U.S. patent application Ser. No. 09/844,818, entitledImproved Efficiency Thermoelectrics Utilizing Thermal Isolation, theprogressive heating and cooling of media in a counter flow configurationas described in FIG. 2, can produce higher thermodynamic efficiency thanunder the same conditions in a single TE module without the benefit ofthe thermal isolation. The configuration shown in FIG. 2, thus presentsan SSCHP system 200 that obtains thermal isolation through the segmentsor stages of heat exchangers sandwiched between thermoelectric modulesin a compact easily producible design.

In addition to the features mentioned above, the thermoelectric modulesthemselves may be constructed to provide thermal isolation in thedirection of media flow and each heat exchanger or some of the heatexchangers may be configured to provide thermal isolation in aindividual heat exchanger through a configuration as will be describedfurther in FIG. 5 or other appropriate configurations. In general, theheat exchanger could be segmented in the direction of flow to provideincreased thermal isolation along the flow of a single TE module such asthe TE module 218 and the inlet heat exchanger 202.

FIG. 3 depicts an array 300 of the same general design as in FIG. 2,consisting of a plurality of TE modules 301 and colder side heatexchangers 302, 305, and 307 connected so that a first working medium315 follows the sequential heat exchanger to heat exchanger path shown.Similarly, a plurality of hot side heat exchangers 309, 311 and 313convey a hotter side working medium 317 in a sequential or staged mannerin the direction shown by the arrows. The TE modules 301 are arrangedand electrically powered as in the description of FIG. 2.

The lower half of FIG. 3 depicts the cold side temperatures ortemperature changes 303, 304, 306, 308 of the colder side working mediumand hot side temperatures 310, 312, 314 of the hotter side workingmedium.

The colder side working medium 315 enters and passes through an inletcolder side heat exchanger 302. The working medium's temperature drop303 in passing through the inlet colder side heat exchanger 302 isindicated by the drop 303 in the cold side temperature curve Tc. Thecolder side working medium 315 is further cooled as it passes throughthe next stage colder side heat exchanger 305, as indicated by atemperature drop 304 and again as it passes through a third colder sideheat exchanger 307, with an accompanying temperature drop 306. Thecolder side working medium 315 exits at colder fluids 316 at temperature308. Similarly, the hotter side working medium 317 enters a first orinlet hotter side heat exchanger 309 and exits at a first temperature310 as indicated by the hotter side temperature curve T_(H) in the FIG.3. The hotter side working medium progresses through the array 300 instages as noted in FIG. 2, getting progressively hotter, finally exitingafter passing through outlet hotter side heat exchanger 313 as hotterworking fluid at 318 and at a hotter temperature 314. It is readily seenthat by increasing the number of stages (that is TE modules and heatexchangers) the amount of cooling and heating power can be increased,the temperature change produced by each heat exchanger can be reduced,and/or the amount of media passing through the array increased. Astaught in the U.S. patent application Ser. No. 09/844,818, efficiencyalso can increase with more stages, albeit at a diminishing rate.

Experiments and the descriptions referenced above, show that thermalisolation and the progressive heating and cooling achievable with theconfiguration of FIGS. 2 and 3 can result in significant efficiencygains, and are therefore important. With such systems, gains of over100% have been achieved in laboratory tests.

FIG. 4A depicts an array 400 with three TE modules 402, four heatexchangers 403 and two conduits 405 configured as described in FIGS. 2and 3. Colder and hotter side working fluids enters at a colder sideinlet 404 and a hotter side inlet 407, respectively and exitrespectively at a colder side exit 406 and a hotter side exit 408. FIG.4B is a more detailed view of one embodiment of a heat exchanger 403. Itis shown as a type suitable for fluid media. The heat exchanger assembly403, has consists of an outer housing 412 with an inlet 410 and an exit411, heat exchanger fins 414, and fluid distribution manifolds 413. Theoperation of array 400 is essentially the same as described in FIGS. 2and 3. The number of the TE modules 402 is three in FIG. 4, but could beany number. Advantageously, the housing 412 is thermally conductive,being made from a suitable material such as corrosion protected copperor aluminum. In one embodiment, heat exchanger fins 414 advantageouslyare folded copper, or aluminum soldered or braised to the housing 412,so as to achieve good thermal conductivity across the interface to theTE Module. The Fins 414 can be of any form, but preferably of a designwell suited to achieve the heat transfer properties desired for thesystem. Detailed design guidelines can be found in “Compact HeatExchangers”, Third Edition by W. M. Kays and A. L. London.Alternatively, any other suitable heat exchangers can be used, such asperforated fins, parallel plates, louvered fins, wire mesh and the like.Such configurations are known to the art, and can be used in any of theconfigurations in any of FIGS. 2 through 11.

FIG. 5A depicts an alternative configuration to that of FIG. 4 for theconduit connections to provide flow from heat exchanger stage to heatexchanger. The array 500 has first and second TE modules 501 and 510,three heat exchangers 502, 503 and 506, and a conduit 504. Of course, aswith previous embodiments and configurations, the particular number oftwo first side heat exchangers 502, 503 and one second side heatexchanger 506 is not restrictive and other numbers could be provided.

FIG. 5B illustrates an enlarged view of a preferred embodiment for theheat exchangers 502, 503, 506. This heat exchanger configuration asshown in FIG. 5B would be appropriate for the other embodiments and canbe used in any of the configuration in FIGS. 2-8 and FIG. 11. Thisadvantageous embodiment for one or more of the heat exchangers in suchconfigurations has an outer housing 516 with segmented heat exchangerfins 511 separated by gaps 513. Working fluid enters through an inlet505 and exits through exit 508. As an alternative to gaps, the heatexchanger could be made so that it is anisotropic such that it isthermally conductive for a section and non-thermally conductive foranother section rather than having actual physical gaps between heatexchanger fins. The point is for thermal isolation to be obtainedbetween stages of an individual heat exchanger segment and anotherindividual heat exchanger segment in the direction of flow. This wouldbe thermal isolation provided in addition to the thermal isolationprovided by having stages of heat exchangers in the embodimentsdescribed in FIGS. 2-5.

Advantageously, a first working fluid fluid 507 which, for example is tobe heated, enters an inlet 505 and passes downward through an inlet orfirst heat exchanger 502 in thermal communication with a first TE module501. The working fluid 507 exits at the bottom and is conducted tosubsequent heat exchanger 503 through conduit 504, where it again passesin a downward direction past a second TE module 510 and exits through asa hotter working 508. Preferably, a second working fluid 517 enters fromthe bottom of FIG. 5A through inlet 518 and travels upward through athird heat exchanger 506 past the colder sides (in the present example)of TE modules 501 and 510. The heat exchanger 506 is in good thermalcommunication with the colder sides of the TE modules 501 and 510. Bythis arrangement, the working fluids 507 and 517 form a counter flowsystem in accordance with the teaching of U.S. patent application Ser.No. 09/844,818, referenced above.

Preferably, the heat exchangers 502, 503 and 506, shown in detail inFIG. 5B, are constructed to have high thermal conductivity from thefaces of the TE modules 501, 510, 510, through the housing 516 and tothe heat exchanger fins 511 (depicted in four isolated segments).However, it is desirable to have low thermal conductivity in thedirection of flow, so as to thermally isolate each heat exchangersegment from the others. If the isolation is significant, and TE modules501 and 510 do not exhibit high internal thermal conductivity in theirvertical direction (direction of working fluid flow), the array 500benefits from the thermal isolation and can operate at higherefficiency. In effect, the array 500 can respond as if it were an arrayconstructed of more TE Modules and more heat exchangers.

FIG. 6 depicts yet another heater/cooler system 600 that is designed tooperate beneficially with working gases. The heater/cooler 600 has TEmodules 601, 602 in good thermal communication with first side heatexchangers 603, 605 and second side heat exchangers 604. A first workingfluid, such as air or other gases 606, is contained by ducts 607, 708,610 and a second working fluid 616 is contained by ducts 615, 613. Fansor pumps 609, 614 are mounted within ducts 608, 615.

The first working fluid 606 enters the system 600 through an inlet duct607. The working fluid 606 passes through a first heat exchanger 603where, for example, it is heated (or cooled). The working fluid 606 thenpasses through the fan 609 which acts to pump the working fluid 606through the duct 608, and through the second heat exchanger 605, whereit is further heated (or cooled), and out an exit duct 610. Similarly, aworking fluid, such as air or another gas, enters through an inlet duct615. It is pushed by a second fan or pump 614 through a third heatexchanger 604 where, in this example, it is cooled (or heated). Thecooled (or heated) working fluid 616 exits through an exit duct 613.

The system 600 can have multiple segments consisting of additional TEmodules and heat exchangers and isolated, segmented heat exchangers asdescribed in FIG. 5B. It can also have multiple fans or pumps to provideadditional pumping force. In addition, one duct, for example 607, 608,can have one fluid and the other duct 613, 615 a second type of gas.Alternately, one side may have a liquid working fluid and the other agas. Thus, the system is not restricted to whether a working medium is afluid or a liquid. Additionally, it should be noted that the exit duct613 could be routed around the fan duct 609.

FIG. 7A depicts a heating and cooling system 700 for beneficial use witha fluid. The assembly has a plurality of TE modules 701 with a pluralityof first side working media 703 and a plurality of second side workingmedia 704. In the present example, both the first side working media 703and the second side working media 704 form disks. The first side workingmedia 703 are attached to a first side shaft 709, and the second sideworking media 704 are attached to a second side shaft 708. The shafts708, 709 are in turn attached to first side motor 706 and second sidemotor 705, respectively, and to corresponding bearings 707. Thepreferred direction of motor rotation is indicated by arrows 710 and711.

A separator 717 both divides the array into two portions and positionsthe TE modules 701. The TE modules 701, held in position by theseparator 717, are spaced so as to alternately sandwich a first sideworking medium 703 and a second side working medium 704. For any two TEmodules 701, the modules are oriented such that their cold sides and hotsides face each other as in the previous embodiments. The working media703, 704 are in good thermal communication with the TE elements 701.Thermal grease or the like is advantageously provided at the interfacebetween the thermoelectric element 701 and the working media 703, 704.The purpose of the grease becomes apparent in the discussion belowregarding the operation of the working media 703, 704. A first sidehousing section 714 and second side housing section 715 contain fluidconditioned by the system 700. Electrical wires 712, 713 connect to theTE modules 701 to provide drive current for the TE modules.

FIG. 7B is a cross sectional view 7B-7B through a portion of the system700 of FIG. 7A. A first fluid 721 and a second fluid 723 are representedalong with their direction of flow by arrows 721 and 723. The firstfluid exits as represented by the arrow 722 and a second exits asrepresented by the arrow 724. The system 700 operates by passing currentthrough electrical wires 712 and 713 to TE modules 701. The TE modules701 have their cold and hot sides facing each other, arranged in thefashion as described in FIGS. 2 and 3. For example, their adjacent coldsides both face the first side working media 703 and their hot sidesface the second side working media 704. The Separator 717 serves thedual function of positioning the TE modules 701 and separating the hotside from the cooled side of the array 700.

For an understanding of operation, assume, for example, that a secondfluid 723 is to be cooled. The cooling occurs by thermal exchange withsecond side media 704. As the second side media 704 rotate, the portionof their surface in contact with the colder side of the TE modules 701at any given time is cooled. As that portion rotates away from the TEmodules 701 through the action of the second motor 705, the second media704 cool the second side fluid that then exits at exit 724. The secondfluid is confined within the array 700 by the housing section 715 andthe separator 717.

Similarly, the first fluid 721 is heated by the first side media 703 inthermal contact with the hotter side of the TE modules 701. Rotation(indicated by arrow 711) moves the heated portion of first media 703 towhere the first fluid 721 can pass through them and be heated viathermal contact. The first fluid 721 is contained between the housing714 and the separator 717 and exits at exit 722.

As mentioned above, thermally conductive grease or liquid metal such asmercury, can be used to provide good thermal contact between the TEmodules 701 and the media 703, 704 at the region of contact.

As mentioned above, the configuration of FIGS. 7A and 7B may also beadvantageously used to cool or heat external components such asmicroprocessors, laser diodes and the like. In such instances, the diskswould contact the part using the thermal grease or liquid metal or thelike to transfer the heat to or from the part.

FIG. 7C depicts a modified version of the system 700 in which the TEmodules 701 are segmented to achieve thermal isolation. FIG. 7C shows adetailed view of the portion of array 700 in which TE modules 701 and702 transfer thermal power to heat moving media 704 and 703 (therotating discs in this example). The moving media 704 and 703 rotateabout axes 733 and 734, respectively.

In one embodiment, advantageously, the working media 704 and 703 rotatein opposite directions as indicated by arrows 710 and 711. As movingmedia 704, 703 rotate, heat transfer from different sections of TEmodules 701 and 702 come into thermal contact with them andincrementally change the temperature of the moving media 704, 703. Forexample, a first TE module 726 heats moving medium 704 at a particularlocation. The material of the moving media 704 at that location movesinto contact with a second TE module 725 as a moving medium 704 rotatescounter clockwise. The same portion of moving medium 704 then moves onto additional TE module segments 701. The opposite action occurs as amoving medium 703 rotates counterclockwise and engages TE modules 701and then substantially TE modules 725 and 726.

Advantageously, moving media 704, 703 have good thermal conductivity inthe radial and axial directions, and poor thermal conductivity in theirangular direction, that is, the direction of motion. With thischaracteristic, the heat transfer from one TE module 725 to another TEmodule 726 by conductivity through the moving media 704 and 708 isminimized, thereby achieving effective thermal isolation.

As an alternative to TE modules or segments 701, 725, 726, a single TEelement or several TE element segments may be substituted. In this case,if the TE elements 701 are very thin compared to their length in thedirection of motion of moving media 704, 703, and have relatively poorthermal conductivity in that direction, they will exhibit effectivethermal isolation over their length. They will conduct heat and thusrespond thermally as if they were constructed of separate TE modules701. This characteristic in combination with low thermal conductivity inthe direction of motion within the moving media 704, 703 can achieveeffective thermal isolation and thereby provides performanceenhancements.

FIG. 7D depicts an alternative configuration for moving media 704, 703in which the media are constructed in the shape of wheels 729 and 732with spokes 727 and 731. In the spaces between spokes 727 and 731 and ingood thermal contact with them, are heat exchanger material 728 and 730.

The system 700 can operate in yet another mode that is depicted in FIG.7D. In this configuration, working fluid (not shown) moves axially alongthe axes of the array 700 passing through moving media 704, 703sequentially from one medium 704 to the next moving medium 704, and soon in an axial direction until it passes through the last medium 704 andexits. Similarly, a separate working fluid, not shown, passes throughindividual moving medium 703 axially through array 700. In thisconfiguration, the ducts 714 and 715 and separator 717 are shaped toform a continuous ring surrounding moving media 704, 703 and separatingmedium 704 from medium 703.

As the working fluid flows axially, thermal power is transferred to theworking fluid through heat exchanger material 728 and 730.Advantageously, the hot side working fluid, for example, passes throughheat exchanger 728, moves through the array 700 in the oppositedirection of the working fluid moving through heat exchanger 730. Inthis mode of operation, the array 700 acts as a counterflow heatexchanger, and a succession of sequential heat exchangers 728 and 730incrementally heat and cool the respective working fluids that passthrough them. As described for FIG. 7C, the thermally active componentscan be TE modules 701 that can be constructed so as to have effectivethermal isolation in the direction of motion of the moving media 704,703. Alternatively, the TE modules 701 and 702 can be segments asdescribed in FIG. 7C. In the latter case, it is further advantageous forthe thermal conductivity of the moving media 704, 703 to be low in thedirection of motion so as to thermally isolate portions of the outerdiscs 729 and 732 of the moving media 704, 703.

Alternately, the design could be further contain radial slots (notshown) in the sections 729 and 732 that are subject to heat transferfrom TE modules 701 and 702 to achieve thermal isolation in thedirection of motion.

FIG. 8 depicts another embodiment of a thermoelectric system an 800having a plurality of TE elements 801 (hatched) and 802 (unhatched)between first side heat exchangers 803 and second side heat exchangers808. A power supply 805 provides current 804 and is connected to heatexchangers 808 via wires 806, 807. The system 800 has conduits and pumpsor fans (not shown) to move hot and cold side working media through thearray 800 as described, for example, in FIGS. 2, 3, 4, 5, 6 and 7.

In this design, the TE modules (having many TE elements) are replaced byTE elements 801 and 802. For example, hatched TE elements 801 may beN-type TE elements and unhatched TE elements 802 may be P-type TEelements. For this design, it is advantageous to configure heatexchangers 803 and 808 so that they have very high electricalconductivity. For example, the housing of the heat exchangers 803, 808and their internal fins or other types of heat exchanger members can bemade of copper or other highly thermal and electrical conductivematerial. Alternately, the heat exchangers 803 and 808 can be in verygood thermal communication with the TE elements 801 and 802, butelectrically isolated. In which case, electrical shunts (not shown) canbe connected to the faces of TE elements 801 and 802 to electricallyconnect them in a fashion similar to that shown in FIG. 1, but with theshunts looped past heat exchangers 803 and 808.

Regardless of the configuration, DC current 804 passing from N-type 801to P-type TE elements 802 will, for example, cool the first side heatexchanger 803 sandwiched between them, and current 804 passing fromP-type TE elements 802 to N-type TE elements 801 will then heat thesecond side heat exchanger 808 sandwiched between them.

The Array 800 can exhibit minimal size and thermal losses since theshunts, substrates and multiple electric connector wires of standard TEmodules can be eliminated or reduced. Further, TE elements 801 and 802can be hetrostructures that accommodate high currents if the componentsare designed to have high electrical conductivity and capacity. In sucha configuration, the array 800 can produce high thermal power densities.

FIG. 9 depicts a thermoelectric system 900 of the same general type asdescribed in FIG. 8, with P-type TE elements 901 and N-type TE elements902 between, and in good thermal contact with first side heat transfermembers 903 and second side heat transfer members 905. In thisconfiguration, the heat transfer members 903 and 905 have the form ofthermally conductive rods or heat pipes. Attached to, and in goodthermal communication with the heat transfer members 903 and 905 areheat exchanger fins 904, 906, or the like. A first conduit 907 confinesthe flow of a first working medium 908 and 909 and a second conduit 914confines the flow of a second working fluid 910 and 911. Electricalconnectors 912 and 913 conduct current to the stack of alternatingP-type and N-type TE elements 901, 902, as described in FIG. 8.

In operation, by way of example, current enters the array 900 throughthe first connector 912, passes through the alternating P-type TEelements 901 (hatched) and N-type TE elements 902 (unhatched) and exitsthrough the second electrical connector 913. In the process, the firstworking media 908 becomes progressively hotter as it is heated byconduction from heat transfer fins 904, which in turn have been heatedby conduction through the first heat transfer members 903. The firstconduit 907 surrounds and confines a first working media 908 exits at achanged temperature as working fluid 909. Portions of the first conduit907 thermally insulate the TE elements 901 and 902 and the second sideheat transfer members 905 from the first (hot in this case) workingmedia 908 and 909. Similarly, the second working media 910 entersthrough the second conduit 914, is cooled (in this example) as it passesthrough the second side heat exchangers 906 and exits as cooled fluid911. The TE elements 901, 902 provide cooling to the second side heattransfer members 905 and hence, to heat exchanger fins 906. The secondside conduit 914 acts to confine the second (cooled in this example)working media 910, and to insulate it from other parts of array 900.

Although described for individual TE elements in the embodiments ofFIGS. 8-9, TE modules may be substituted for the TE elements 901, 902.In addition, in certain circumstances, it may be advantageous toelectrically isolate TE elements 901, 902 from the heat transfer members903, 905, and pass current through shunts (not shown). Also, the heatexchangers 904, 906 can be of any design that is advantageous to thefunction of the system. As with the other embodiments, it is seen thatthe configurations of FIGS. 8 and 9 provide a relatively easilymanufacturable system that also provides enhanced efficiency fromthermal isolation. For example, in FIG. 8, the heat exchangers 808, 803which alternate between P-type and N-type thermal electric elements,will either be of the colder or hotter heat exchanger type, but will bereasonably thermally isolated from each other and cause thethermoelectric elements of the P and N type to be reasonably thermallyisolated from one another.

FIG. 10 depicts another thermoelectric array system (1000) that providesthermal isolation. Advantageously, this configuration may perform thefunction of a system that utilizes cooling and heating of the samemedium to dehumidify, or remove precipitates, mist, condensable vapors,reaction products and the like and return the medium to somewhat aboveits original temperature.

The system 1000 consists of a stack of alternating P-type TE elements1001 and N-type TE elements 1002 with interspersed cold side heattransfer elements 1003 and hot side heat transfer elements 1004. In thedepicted embodiment, heat exchanger fins 1005, 1006 are provided forboth the colder side heat transfer elements 1003 and the hotter sideheat transfer elements 1004. A colder side conduit 1018 hotter sideconduit 1019 direct working fluid 1007, 1008 and 1009 within the array1000. A fan 1010 pulls the working fluid 1007, 1008 and 1009 through thearray 1000. Preferably, colder side insulation 1012 thermally isolatesthe working fluid 1007 while travelling through the colder side from theTE element stack and hotter side insulation 1020 preferably isolates theworking fluid while travelling through the hotter side from the TEelement stack. A baffle 1010 or the like separates the colder and hottersides. In one preferred embodiment, the baffle 1010 has passages 1010for working fluids 1021 to pass through. Similarly, in one embodiment,fluid passages 1017 allow fluid 1016 to enter the hot side flow passage.

A screen 1011 or other porous working fluid flow restrictor separatesthe colder from the hotter side of array 1000. Condensate, solidprecipitate, liquids and the like 1013 accumulate at the bottom of thearray 1000, and can pass through a valve 1014 and out a spout 1015.

Current flow (not shown) through TE elements 1001 and 1002, cools colderside heat transfer elements 1003 and heats hotter side heat transferelements 1004, as discussed in the description of FIG. 9. In operation,as the working fluid 1007 passes down the colder side, precipitate,moisture or other condensate 1013 from the working fluid 1007 cancollect at the bottom of the array 1000. As required, the valve 1014 canbe opened and the precipitate, moisture or condensate 1013 can beremoved through the spout 1015 or extracted by any other suitable means.

Advantageously, some of the working fluid 1021 can be passed from thecolder to the hotter side through bypass passages 1020. With thisdesign, not all of the colder side fluid 1007 passes through the flowrestrictor 1011, but instead can be used to reduce locally thetemperature of the hotter side working fluid, and thereby improve thethermodynamic efficiency of the array 1000 under some circumstances.Proper proportioning of flow between bypass passages 1020 and flowrestrictor 1011, is achieved by suitable design of the flow propertiesof the system. For example, valves can be incorporated to control flowand specific passages can be opened or shut off. In some uses, the flowrestrictor 1011 may also act as a filter to remove precipitates fromliquid or gaseous working fluids 1008, or mist or fog from gaseousworking fluids 1008.

Advantageously, additional hotter side coolant 1016 can enter array 1000through side passages 1017, also for the purpose of reducing the hotterside working fluid temperature or increasing array 1000 efficiency.

This configuration can produce very cold conditions at the flowrestrictor 1011, so that working fluid 1008 can have substantial amountsof precipitate, condensate or moisture removal capability. In analternative mode of operation, power to the fan 1010 can be reversed andthe system operated so as to heat the working fluid and return it to acool state. This can be advantageous for removing reaction products,precipitates, condensates, moisture and the like that is formed by theheating process. In one advantageous embodiment, flow restrictor 1011,and/or heat exchangers 1005 and 1006 can have catalytic properties toenhance, modify, enable, prevent or otherwise affect processes thatcould occur in the system. For liquid working fluids, one or more pumpscan replace fan/motor 1010 to achieve advantageous performance.

FIG. 11 depicts a thermoelectric array 1100 similar in design to that ofFIGS. 2 and 3, but in which working media has alternate paths throughthe system. The array 1100 has TE modules 1101 interdispersed betweenheat exchangers 1102. A plurality of inlet ports 1103, 1105 and 1107conduct working media through the array 1100. A plurality of exit ports1104, 1106 and 1108 conduct working media from the array 1100.

In operation, by way of example, working media to be cooled enters at afirst inlet port 1103 and passes through several of the heat exchangers1102, thereby progressively cooling (in this example), and exits througha first exit port 1104. A portion of the working media that removes heatfrom array 1100 enters through a second inlet port 1105, passes throughheat exchangers 1102, is progressively heated in the process, and exitsthrough a second exit port 1106.

A second portion of working media to remove heat enters a third inletport 1107, is heated as it passes through some of the heat exchangers1102 and exits through a third exit port 1108.

This design allows the cool side working media which passes from thefirst inlet port 1103 to the first exit port 1104 to be efficientlycooled, since the hot side working media enters at two locations in thisexample, and the resultant temperature differential across the TEmodules 1101 can be on average lower than if working media entered at asingle port. If the average temperature gradient is lower on average,then under most circumstances, the resultant system efficiency will behigher. The relative flow rates through the second and third inlet port1105 and 1107 can be adjusted to achieve desired performance or torespond to changing external conditions. By way of example, higher flowrates through the third inlet port 1107, and most effectively, areversal of the direction of flow through that portion so that thirdexit port 1108 is the inlet, can produce colder outlet temperatures inthe cold side working media that exits at first exit port 1104. All ofthese variations.

It should also be noted that the features described above may becombined, without departing from the invention.

The above examples have been discussed in terms of cooling and heatingof working media by applying power to TE elements and modules. Thereverse process of extracting electrical power by applying temperaturegradients across the TE elements and modules is well known to the art.In particular, the configuration shown in FIGS. 2, 3, 4, 5, 6, 7, 8, 9and 11 lend themselves to power generation.

In general, the systems described in these figures do operate in bothmodes. Advantageously, specific changes can be implemented to optimizeperformance for cooling, heating or power generation. For example, largetemperature differentials (200 to 2000° F.) are desirable to achievehigh-efficiency in power generation as is well know in the art, whilesmall temperature differentials (10 to 60° F.) are characteristic ofcooling and heating systems. Large temperature differentials requiredifferent construction materials and possibly TE modules and elements ofdifferent design and materials. Nevertheless, the basic concept remainsthe same for the different modes of operation. The designs described inFIGS. 5, 8 and 9 are advantageous for power generation because theyoffer the potential to be simple, rugged, low-cost design andfabrication. However, all of the above mentioned designs can have meritfor specific power generation applications and cannot be excluded.

Although several examples have been illustrated, as discussed above, thedescription above is merely illustrative of broad concepts of theinventions, which are set forth in the attached claims. In the claims,all terms are attributed to their ordinary and accustomed meaning andthe description above does not restrict the terms to any special orspecifically defined means unless specifically articulated.

1. An improved thermoelectric system comprising: a plurality ofthermoelectric modules, at least some of which are substantiallythermally isolated from each other, each module having a hotter side anda colder side; and at least one solid movable working medium in thermalcommunication with at least two of the plurality of thermoelectricmodules in sequence, such that the working medium is progressivelycooled or heated in stages by at least two of the plurality ofthermoelectric modules, the working medium movable relative to at leasttwo of the plurality of thermoelectric modules as the working medium iscooled or heated.
 2. The thermoelectric system of claim 1, wherein theworking medium comprises a plurality of disk-like media mounted to arotating shaft, and said media form a stacked configuration with thethermoelectric modules sandwiching at least some of the disk-like media.3. The thermoelectric system of claim 1, wherein the working mediumcomprises a plurality of working media forming an alternating stackedconfiguration of thermoelectric modules and working media.
 4. Thethermoelectric system of claim 3, wherein the working mediasubstantially thermally isolate at least some of the plurality ofthermoelectric modules.
 5. An improved thermoelectric system comprising:a plurality of thermoelectric modules, at least some of which aresubstantially thermally isolated from each other, the plurality ofthermoelectric modules comprising at least one N-type thermoelectricelement and at least one P-type thermoelectric element, eachthermoelectric module having a hotter side and a colder side; and aplurality of heat transfer devices, at least some of which are indifferent planes and in thermal communication with at least one of theplurality of thermoelectric modules, at least two of the heat transferdevices fluidly coupled together and accepting a first working fluidthat flows sequentially through the at least two heat transfer devices,wherein the first working fluid is cooled or heated in stages as itflows through the at least two heat transfer devices.
 6. Thethermoelectric system of claim 5, wherein each of at least some of theheat transfer devices are sandwiched between at least two thermoelectricmodules.
 7. The thermoelectric system of claim 6, wherein at least oneof the plurality of thermoelectric modules has its cooler side facing asandwiched heat transfer device.
 8. The thermoelectric system of claim5, wherein the thermoelectric modules and heat transfer devices form astack, with the cooler sides of at least some of the thermoelectricmodules generally facing one another, separated by at least one heattransfer device, and the hotter sides of at least some of thethermoelectric modules generally facing one another, separated by atleast one heat transfer device.
 9. The thermoelectric system of claim 5,wherein the heat transfer devices are heat exchangers comprising ahousing and heat exchanger fins, the heat exchanger fins of a heatexchanger forming stages in the direction of the working fluid flow, soas to provide additional thermal isolation for at least one of thethermoelectric modules in thermal communication with the heat exchanger.10. The thermoelectric system of claim 5, wherein the first workingfluid flows in the same direction through each of the cooling heattransfer devices.
 11. The thermoelectric system of claim 8, wherein theheat transfer devices accept a working fluid to flow through them in adefined direction.
 12. The thermoelectric system of claim 11, whereinthe heat transfer devices are heat exchangers comprising a housing withheat exchanger elements inside formed in segments, and wherein at leastone of the segments is substantially thermally isolated from at leastone other of the segments.
 13. The thermoelectric system of claim 12,further comprising at least one conduit providing a fluid path from afirst heat exchanger to a second heat exchanger, such that working fluidtravelling through the first heat exchanger and the second heatexchanger is cooled or heated in stages.